1. Technical Field
The present description relates to communications with mobile communication devices that roam from a home region of a communications network to a visited region of the same or different communications network.
2. Background
Communications networks are widely known and used in commerce. A network node is a device or computer system connected by communication links in the network. Information is exchanged between network nodes according to one or more of many well known, new or still developing protocols. In this context, a protocol consists of a set of rules defining how the nodes interact with each other based on information sent over the communication links. A protocol-specific process executing on a node receives the information sent according to the protocol and acts based on the received information.
A publicized next generation network architecture for wireless mobile telecommunications networks that uses the widely supported Internet Protocol (IP) is called Advances to Internet Protocol (IP) multimedia subsystem (A-IMS). A-IMS supports the development of a wide range of multimedia services between communications devices, including real-time voice, video and data, over both mobile and fixed devices. The end point of an A-IMS communication is called a terminal, and includes both fixed and mobile computers, telephones, cell phones, and personal digital assistants (PDAs), among others.
As is well known to even the casual user of a mobile terminal, as the mobile terminal is moved from one location to another, the user may leave the area of the user's home wireless network service provider, for whom the user is a subscriber, and enter the area serviced by another wireless network service provider, called the visited network. While in the area of the visited network, the mobile terminal is said to be roaming. Different rates may apply and the subscriber may notice differences in data services provided.